Although the cost effectiveness of screening with filter paper dried blood spots (DBS) has been recognized all over the world in new born screening programs, the methodology has not been applied to screening other age groups. Even for tests such as TSH which can be used to detect hypothyroidism in adults as well as newborns, the newborn screening programs do not include adult samples in their protocols because of large age related differences in hormone levels. Other tests useful for screening adults are not used in newborn screening programs. The investigators propose to develop an adult screening program using DBS to allow early identification of treatable diseases such as primary hypothyroidism that are often misdiagnosed or not recognized because of nonspecific symptoms. A TSH assay will be adapted to detect hypothyroidism in adults, and the assay will be validated with parallel collection of serum and DBS from 200 patients. Normal values for DBS samples will be determined for different age groups. An assay for thyroid peroxidase antibody will be adapted for use with DBS, and its application as a screening assay for hypothyroidism in women during the first four months postpartum investigated. Additional DBS assays will be developed in Phase II.